Turkey necks change from red to blue to white, a trait that inspired a new tool to detect toxins in the environment. (Photo: Shutterstock)

Scientists at the UC Berkeley are making a biosensor designed to change color in the presence of certain chemicals, inspired by a characteristic inherent in turkey skin. Turkeys have a strange power: they can dramatically change the color of their heads from whites to blues to reds and back again. The underlying mechanism of the swift change in color is the swelling and contracting of blood vessels — but that, in turn, is dependent on their psychological states of excitement or stress.

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More specifically, when these birds are under duress or excited, the bundles of collagen fibers interspersed through their swelling or contracting blood vessels alters the scattering of light waves, causing the perception of the changing colors of their head. The biosensor that the UC Berkeley bioengineers are planning to make will mimic this mechanism. The sensor is designed to change color in response to certain chemicals, and includes a companion app that can report on chemicals present based on an analysis of color changes.

The scientists expect the sensor in smart phones to be used in a variety of settings. It can be easily used as a toxin detector, for instance. "Our system is convenient, and it is cheap to make," said Seung-Wuk Lee, UC Berkeley associate professor of bioengineering who led the team. "In the future, we could potentially use this same technology to create a breath test to detect cancer and other diseases."

A few years ago, the same research team had developed a technique that can help assemble structures that mimic collagen fibers. In this study, published in the journal Nature Communications, the researchers used a benign virus as an engineering tool to manufacture tunable material with optical, biomedical, and mechanical properties. The viruses actually behaved like molecular Legos with the ability to fine tune their shapes to perform different functions. In course of the study, the scientists found that tightly bundled nanostructures, as they contracted and expanded, could affect color.

In their study, the study team found that specific color patterns emerged when biosensors were exposed to volatile organic compounds. The compounds exposed to range from isopropyl alcohol and methane to TNT. The sensors were sensitive enough to detect concentrations as low as 300 parts per billion. In addition, humidity between 20 and 90 percent also impacted color change. While the color turned red with rising humidity, it turned blue as humidity dropped.

The researchers are currently working on to make sensors widely available for which they will build iColor Analyzer app which can translate the results of the sensor's color bands. The principle used in the biosensor, according to Lee can be used to detect several diseases including diabetes and cancers. However, it will be few more years before the product comes to the market.